1. Field of Invention
The present invention relates to a filament lamp used for the heat treatment of a semiconductor wafer, solar cell or liquid crystal that provides a uniform distribution of light.
2. Description of Related Art
A light irradiation-type heat treatment device in the semiconductor manufacturing process has widely been used in the fields of film formation, diffusion and annealing. All of these heat treatment devices are capable of rapidly heating a semiconductor wafer or other plate-like object such that the temperature can be increased to 1000° C. or above within several seconds to several tens of seconds. There is a need for increasing the temperature at a faster speed recently, and consequently a need for increasing the amount of electric power inputted into such heat treatment devices during the time of the heat treatment. This is referred to as a spike anneal in which the temperature is increased at a high speed exceeding 200° C./second and brought down immediately after a desired temperature has been achieved. The spike anneal enables the formation of a very thin diffusion layer (shallow junction) in the semiconductor wafer, thereby enhancing the efficiency of a semiconductor element manufactured on the wafer.
If the temperature distribution of a semiconductor wafer should become nonuniform at the time of heating, a phenomenon referred to as slip occurs to the semiconductor wafer. In other words, a defect caused by crystal transition occurs, which may lead to a defective product. It is therefore necessary to use a light irradiation-type heat treatment device for heating, maintaining a high temperature of, and cooling a semiconductor wafer when thermally treating a semiconductor wafer. To provide such a uniform distribution of temperature, Japanese Laid-open Application No. 2006-279008 (corresponding to US 2006/0197454 A1) discloses a filament lamp provided with multiple leads capable of independently supplying electric power to multiple filaments in one luminous tube. This design allows adjustment of the amount of electric power inputted into the multiple filaments, thereby allowing the distribution of temperature over an area to be adjusted to a highly uniform pattern.
FIGS. 10(a) and 10(b) illustrate a conventional filament lamp 1. FIG. 10(a) shows a perspective view of the entire filament lamp 1. FIG. 10(b) shows a sectional view taken by the A-A′ line as shown in FIG. 10(a).
A straight-shaped luminous tube 2 has an elliptical cross section, and its both ends are air-tightly sealed with sealing parts 3a and 3b. Inside the luminous tube 2, coil-shaped filaments 12a and 12b are provided with multiple ring supporters 12ar and 12br. Ring supporters 12ar and 12br are spaced lengthwise and are sequentially disposed in the axial direction of the luminous tube 2. Both ends of the filaments 12a and 12b are linked with internal leads 13a, 13b, 13c and 13d for supplying electric power. The internal leads 13b and 13d are each covered with an insulating narrow tube made of, for example, quartz glass so that they do not short-circuit to the filaments 12a or 12b through the ring supporters.
The internal leads 13a, 13b, 13c, and 13d connected to the abovementioned filaments 12a and 12b extend to the sealing parts 3a and 3b on both ends and are electrically connected to external leads 14a, 14b, 14c, and 14d individually via metal foils 11a, 11b, 11c, and 11d, respectively. In other words, the internal leads 13a and 13b extended to one end side of the filaments 12a and 12b respectively are electrically connected to the external leads 14a and 14b on one end side via the metal foils 11a and 11b at the sealing part 3a on one end side, respectively. Similarly, the internal leads 13c and 13d extended to the other end side are electrically connected to the external leads 14c and 14d on the other end side via the metal foils 11c and 11d at the sealing part 3b on the other end side, respectively.
As shown in FIG. 10, the filaments 12a and 12b are disposed in parallel with the internal leads 13b and 13d in order to independently supply electric power to the filaments 12a and 12b inside the luminous tube 2. The internal leads 13b and 13d are insulated from the filaments 12a and 12b by covering them with insulating narrow tubes 8a and 8b. As shown in FIG. 10(b), the filament 12a is positioned inside the luminous tube 2 with a ring supporter 12ar that is brought into contact with the inner wall of the luminous tube 2.
However, the applicants have observed that the internal lead 13b covered with the narrow tube 8a protrudes from the inner wall of the smooth luminous tube 2, and therefore may engage the ring supporter 12ar. In response to such engagement, the ring supporter 12ar might move to either the right or the left in order to expand into a broader space. If the ring supporter 12ar deviates from its position, the position of the filament 12a also moves. As a result, there may occur a problem in that the distribution of light generated toward an object to be treated may be changed into a nonuniform pattern.